Photoelectric converter



March 16, 1937. 1.. J. ANDRES 2,073,773

' PHOTOELECTRIC qoNvERTER Filed Sept. 27} 1935 by fltty Patented Mar. 16, 1937 UNITED STATES PATENT OFFICE Application September 27, 1933, Serial No. 691,175

2 Claims.

This invention relates to means for transposing an image into electrical energy, and more particularly, for reproducing the original from the photographic record of sound waves, mechanical 5 movements, or other such events.

This invention will be herein described as embodied inthe reproducer of a sound record which is recorded in a track on a motion picture film. The sound isphotographed in a narrow track 10 which is, by one common method, of variable density, where the sound vibrations are impressed upon a variable light source. By another common method, the sound is recorded by oscillating means with the result that the track varies in 1:, Width.

In reproducing the sound, a ribbon of light is directed into a photo cell and the light is brought into moving relation with the sound track so that its intensity or width, or the amount of light is afiected thereby so as to correspond with the sound vibrations.

In order to prevent overlapping of the sound phases, and distortion, it is essential that the light beam or ribbon be verythin where it comes into relation with the track. Also, it is an advantage to have the area of the beam increased as it comes into relation with the light sensitive electrical control element, after it leaves the image.

Heretofore, such mechanism involved optical lenses and mechanical apertures and consequent- 1y have required exceedingly accurate and fine adjustments in order to obtain the desired. thinness and intensity and to obtain the requisite 35 focusing. Therefore, a main object of this invention is to provide a simplified device in which less accuracy of construction and adjustment is required; also to substantially eliminate the necessity of close focusing; and to obviate the neces- 40 sity of using a specially constructed lamp for the light source.

Other objects, and this invention will become apparent inthe following description, with reference to the accompanying drawing in which an 45 illustrative embodiment of this invention is shown;

In the accompanying drawing: Fig. 1 is a diagrammatic view of thedevice. Fig. 2 is a perspective view of the prism shown 50 in Fig. 1.

shown, the film being moved over a fixed supporting plate 6 which has a suitable aperture I.

Between the plate 6 and the lamp 3 is fixedly mounted a prism 8 which collects unfocused rays of light from the source and directs a large portion of the rays in a thin ribbon beam of light 9; thru the portion of the film on which the sound is recorded, and into the cell 4. The cross section of the prism is a right angle triangle, and the base I0 which is exposed to the light is rectangular. On the base is formed a fine linear grid screen I I for collecting and breaking up the light rays. In practice, this screen is formed by grooving the surface of the prism in a thousand or more lines per inch.

The sides l2 and I3 of the prism are opaquely coated, as well as the ends I4 and I5 which are inclined so as to reduced the length of the apex l6 which is left uncoated. In"'practice, the apex is ground to remove the coating, but the area of the surface is made as narrow as possible so that its actual width is about one half a thousandth of one inch.

The screen H will collect light rays coming from various directions, and a large portion of th rays striking on the screen are deflected in the interior of the prism and reflected out thru the apex. Accordingly, the beam is polarized within a small angle, and the area increases somewhat with the distance from the point of emission. Therefore, the screen 5 is passed very close to the apex but does not have to be in contact as has been required in prior devices and caused either scratching .of the film or the glass.

By this arrangement nearly any ordinary form of lamp which gives off a steady light, may be used, and no special accuracy is required in the relation of the lamp to the prism. Obviously, the location of the screen with respect to the prism is not particularly delicate so that no close adjustments are needed. Also the beam may be reflected by the image, or passed thru as shown and the one arrangement is applicable to either the variable density, or the oscillating form of sound track.

Having thus described my invention I claim:

1. The combination in a sound reproducer, an optical system consisting of an ordinary constant voltage lamp, a triangular prism having a rectangular base exposed to the light, a fine grid screen formed on the base, the ends of the prism being inclined to reduce the length of the apex and the sides and the ends of the prism being coated to direct a large portion of the rays striking the base thru the apex in a thin beam light.

purposes consisting only of an ordinary electric lamp for a source of light, a, triangular prism having a grating formed on its base, the sides and ends of the prism being opaquely coated, means for guiding a film having a track of images thereon in close proximity to the apex of the prism, and a photoelecric cell for receiving the beam 5 after it passes the film.

LLOYD J. ANDRES. 

